Battery electric vehicles (BEV's) and plug in hybrid electric vehicles (PHEV's) (collectively referred to as EVs or xEVs) may use an electric motor as their primary or only source of motive power. A BEV or PHEV typically requires an external power source in order to charge the vehicle mounted battery pack which powers the motor.
Increasing popularity and sales of battery electric vehicles (BEV's) and plug in hybrid electric vehicles (PHEV's) have led to advances in vehicle and charging system technology. The use of a charge cord to plug a vehicle into a power grid may be viewed as an inconvenience by potential BEV and PHEV owners. One way to allow the charging of a vehicle without having to physically plug the vehicle into a power grid is through the use of an inductive wireless charging system. Such inductive wireless charging systems are commonly used in electronic devices such as electric toothbrushes and cell phones. Inductive wireless charging systems are now being proposed for charging BEVs and PHEVs.
Inductive wireless charging uses an electromagnetic field to transfer energy from a transmitting coil on the ground to a receiving coil attached to the vehicle. The receiving coil required to charge a vehicle is much larger than what is required to charge a cell phone or a toothbrush. Larger coils can transfer more energy than smaller ones. It is often difficult to find enough room to package a large receiving coil under a vehicle.
The proximity of the two coils affects the efficiency of the energy transfer. It is desirable to locate the receiving coil along the center of the vehicle, so the operator can more easily park the vehicle over the transmitting coil. Locating the receiving coil in the center of the vehicle also keeps the operator and passersby away from the electromagnetic field generated by these large inductive charging coils. This further reduces options for easily packaging the transmitting coil on the underside of a vehicle.